TESTING CENTER DIFF LOCK SWITCH/HARNESS

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I recently re-installed the center diff lock switch on my 97 FZJ80 and noticed that it no longer engages the center diff nor does the diff lock light come on on the dash. I think the problem is either the switch or the wiring harness it plugs into. I’m under the impression that the diff lock switch (when depressed) completes a circuit – which sends a signal to the diff lock actuator and activates the diff lock light on the dash as well. So, to determine if if the harness is broken I’d assume that a small piece of wire put in the correct pins would complete the circuit and activate the diff lock and light ? Assuming this is correct, does anyone know which pins (in the harness) to put the wire into to test the harness thus engaging the actuator and activating the light ? Or perhaps there is a better method ? :dunno:
 
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Matt -

Removing the switch from the circuit and shorting the #7 and #10 pins on the jack; then engaging low range on the transfer case - be sure the harness is plugged in to the transfer case under the truck - should engage the actuator as you described. This will at least tell you if the switch is the culprit.

If the pins are not labeled, hold the jack on the end of the harness facing you, with the alignment keyway up... on the bottom row, counting from the left - it's the 3rd and 6th (last) pin in the jack.

Good luck!

R -
 
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Ok, I really need to buy a shop manual.

So if the female terminal connector is facing us it goes:


1 2 3 4 5
6 (7) 8 9 (10)

and connecting 7 and 10 will do the job ?
 
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M -

Assuming the keyway is at the top, the female end looks, and counts like this:

 1 2         3   4
 5 6 (7) 8 9 (10)

...and yes, the stock shorting plug connects 7 & 10.

R -
 
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I took apart the dash and connected # 7 and 10 pins and nothing happened. But, when I connected #8 and #10 I got a click. No light on the dash or sound of the actuator which was always apparent.

As per Cruiserdan's instructions to disconnect the diff in low (on another thread), I have snipped the #7 wire on the relay behind the ECU. So, now I can put it in low without the diff locking. I have a 1997 though, so is the wiring the same ? Perhaps this could be part of the problem - different wiring ? :dunno: Any suggestions ?
 
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M -

  As Beo and others have pointed out so many times before, it helps to be aware of the details & modifications when troubleshooting. The suggestion I made - given that your #7 wire on the tranny relay is disconnected - was of no value, as you have discovered.

 You can still work this out, it will just be a bit more difficult...

 1. Mine is also a '97, and I have also disconnected #7 on the tranny relay. The diff switch &  locking mechanism both work properly, so that is not likely the source of your problem. However...

  2. It would not hurt to double check that the correct wire was disconnected. The one you want is a small gauge, black wire with a blue tracer. If something else was disconnected accidentaly, the results would be unpredictable.

  3. The diff switch and harness do not appear in the U.S. spec wiring diagrams (except for the shorting pin), so there is no way to advise as to the "pin-outs" on the harness plug. About the only thing you can do is to put a multimeter on the individual switch pins, each combination in turn while working the switch, to determine which pins function as "on : off" .

  Keep in mind there are three separate switching functions:
  a. Back-lighting when the headlights are on
  b. Diff lock indicator light in the instrument cluster
  c. Diff lock actuator itself

  You need to determine which pins control "b" and "c" and short the corresponding pins on the harness plug to verify their proper function, and to isolate the switch as the culprit/or not the culprit.

  Electrical troubleshooting is tedious, especially when you do not have all of the information.  :p I will hopefully have an Oz spec wiring diagram in the near future. If you have not solved this problem by then, I'll be glad to look this up for you.

 Hope some of this helps.  Good luck!

 R -
 
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Gentlemen:

Thank you for all of the help. I will attempt to isolate the problem with a multimeter and post how it went.

Matt
 
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I disconnected the center diff lock switch, reconnected the #7 pin wire and disconnected the battery for good measure to reset the ECU. Took it for a test drive, put it in all gears in low and got no light on the dash nor a locked diff. I checked all fuses as well and none were blown out. The center diff lock was working fine prior to cutting the #7 pin. I don't know what to make of it. Severe frustration ensues.
 
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Matt -

Been there, done that. Patience, and we'll get this solved.

&nbsp:Did you replace the factory shorting plug on the center diff harness plug - after removing the center diff switch - before your test drive??

R -
 
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I'm not quite sure what the factory shorting pin is. I did check all of the pins on the diff lock switch harness to make sure they were secure though. I checked all fuses again as well. Could there be a fuse on the harness wiring itself ?

Is it at all possible that I messed something up on the transfer case relay when pulling it out ?
 
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I think Paradise is talking about the plug with the jumper wire that was originaly in the harness where you installed,then removed the centerdifflock switch...
if you dont have the centerdifflock switch in place,then there shoud be a plug there that has one jumper wire in it...see it here
difflock%20jumper%20plug%20front.jpg


and here:
difflock%20jumper%20plug%20rear.jpg


that plug/jumper has to be there(or the switch to activate it)in order for the system to work properly....
sorry for the poor picture quality ,i just took this camera out of the box and loaded the drivr/snapped off the two shots and uploaded them to my server space,and i havent played with this camera yet,its a cheapy though,just to take on the boat and stuff,i will get better(i hope)

doug
 
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Ok - I see. I'll go back to the garage and take apart the dash again. Now I know what I'm looking for.

This just may be the problem.
 
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It appears that the #7 and #10 pins have been spliced together with the blue thing in the pic. It looks like that may be in place of the factory shorting plug ? I had an issue with the switch about a year ago and Toyota must have put the blue splice in. But, that should let the diff work in low correct ? ???
 
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Ok - I'll do this. I hope you're not talking about the main ECU being fried. You're talking about the diff relay ECU right ?
 

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